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CaseStudySolutions

This appendix contains the solutions to the Acme Mining Company

Case Study.

Sun Proprietary: Internal Use Only 1Copyright 2000 Sun Microsystems, Inc. All Rights Reserved. Enterprise Services March 2000, Revision B

The Acme Mining Company

Rewritten Problem Statement

Note – The candidate classes and objects have been underlined.

The Acme Mining Company requires a computerized payroll system.

They need the system to operate on two planets where they currently

trade. Planet Earth and the Planet Zog are the locations, each has a

differing currency with different tax and deduction policies.

Pay is calculated periodically, this is currently monthly and weekly

dependant on the pay type of the employee.

Currently the pay types are monthly paid, weekly paid and hourly

paid employees.

Monthly paid employees have an annual salary divided into twelve

equal amounts, these are paid at the end of each month.

Weekly paid employees are paid their weekly rate of pay at the end of

each calendar week.

Hourly paid employees have an hourly rate of pay. The hours worked

by these employees are determined by a clock in, and clock out time,

recorded by a time clock system. The excess hours worked, above the

normal site working hours are paid at an overtime rate applicable to

their site.

The majority of Acme employees are hourly paid.

The time clock information for hourly employees can be downloaded

directly from the time clock. This must be done once every 24 hours.

Employees are identified by their name and their employee

identification number only.

Weekly paid and hourly paid employees can elect to be paid in cash or

by check. Monthly paid employees can only be paid by cheque. All

payments are paid in the local currency applicable to the planet.

2 Object-Oriented Application Analysis and Design for Java Technology (UML)Copyright 2000 Sun Microsystems, Inc. All Rights Reserved. Enterprise Services March 2000, Revision B

These are currently, on Planet Earth, Earth Dollars and on Planet Zog,

Zog Groats. Pay is calculated by applying any tax deductions (that

apply to the location) to every employee and company deductions that

apply to an employee. Taxes are cumulative for the financial year.

The Planet and Country taxes are paid on the gross salary at tiered

rates. The Social Security and Pollution taxes are paid on the gross

salary and are at a fixed rate. Other deductions applicable are for

Health Insurance, which is optional. The Pension Scheme however, is

compulsory for all employees. Pensions are deducted at a flat

percentage rate.

Pay rates and employee details can only be recorded and amended by

Human Resources. Weekly and Monthly Payroll runs are both initiated

by the payroll clerk, it produces payslips itemizing the amount paid

and any deductions made to each employee.

It produces a summarized list of payments and deductions made to

each employee for each run. This summary shows total deductions

collected from all employees for each deduction and tax. After the end

of the tax year the Payroll Clerk will request a summary of tax paid by

all employees for that tax year.

Current Taxes Applicable: Planet Tax, Country Tax, Pollution Tax, and

Social Security Tax.

Planet Earth Taxes: Pollution Tax, Planet Tax, and Country Tax.

Planet Zog Taxes: Planet Tax, and Social Security Tax.

Case Study Solutions 3Copyright 2000 Sun Microsystems, Inc. All Rights Reserved. Enterprise Services March 2000, Revision B

Data Dictionary

Word/Phrase Definition

Payroll Run Manually initiated request forcalculations of pay and deductions foreach employee applicable to specificrun.

Monthly Payroll Run Payroll Run only applicable formonthly employees.

Weekly Payroll Run Payroll Run only applicable for weeklyand hourly employees

Employee I.D.Number

A number uniquely identifies theemployee within the company

Zog Groats Currency applicable to Planet Zog

Earth Dollars Currency applicable to Planet Earth

Time Clock A System which records time forcommencement and completion ofemployees work hours. Data is stored,it can be printed or downloaded toanother system.

Monthly Employee Paid on a monthly basis, dividing thepayments into twelve equalinstallments

Hourly Employee Paid by hourly rate for each hourworked according to the specific rateallocated to the individual employee.Subject to overtime payment foradditional hours worked at companyand location rate.

Taxation Tax deductions applied on grossearning. It is a banding system, wheretax is paid at a specified rate forearnings up to a band limit. Anyincome in that band is taxed in thenext band, so forth.


Tiered Rate Tax A deduction that is applied at thespecified percentage rate on grossearnings.

Percentage RateDeduction

A fixed amount deducted at every payperiod.

Flat Rate Tax

Word/Phrase Definition


Use Case


Use Case Scenarios

Monthly Run Scenario I

1. The Payroll Clerk on the Planet Zog selects a Payroll Run.

2. They select the monthly run from the options.

3. All monthly paid employees are selected.

4. The first employee is selected.

5. Their monthly pay is calculated.

6. Their gross pay to date is calculated.

7. Planet Tax is calculated.

8. Social Security Tax is calculated.

9. Pension deduction is calculated.

10. This employee has the health insurance option, so

this is calculated.

11. The net pay is calculated.

12. The payslip is printed.

13. All deductions are accumulated.

14. Next Employee is selected,

15. All as above, exception this employee has no Health Insurance

16. No more employees

17. Print total deductions.


Monthly Run Scenario 2

1. The Payroll Clerk on the Planet Zog selects a Payroll Run.

2. They select the monthly run from the options.

3. All monthly paid employees are selected.

4. No Employees found.


Add Employee Scenario 1

1. Human Resources on the planet Zog log on to the system.

2. They select enter new employee from the menu

3. New Employee Screen Displayed.

4. The enter employee John Simms for the name and 1023 for the

employeeID.

5. System check for identical ID, none found.

6. Further details are requested.

7. They choose the monthly pay type form menu.

8. They are asked to enter monthly salary in Zog Groats.

9. They enter 30500.

10. The are asked to enter starting date.

11. They enter 03/05/2049.

12. They are asked if the employee requires the Health Insurance

option.

13. They select Yes.

14. Employee Details are added to the system.


Add Employee Scenario 2

1. Human Resources on the planet Zog log on to the system.

2. They select enter new employee from the menu

3. New Employee Screen Displayed.

4. The enter employee Peter Smithy for the name and 101 for the

employed

5. System checks for identical ID.

6. Identical ID found

7. User requested to enter ID again.


Use Case Forms

Use Case Form: Monthly Run

Name Monthly Run

Actor payroll Clerk/Human Resources

Priority Low

Status To be agreed

ExtensionPoints

None

Extends None

Includes Payroll Run

Preconditions/Assumptions

Post-conditions

Flow of Events 1. Use Case begins when initiated by actor2. Employees of Type Monthly are selected3. Include (Payroll Run)

AlternativePaths

Non-functional Requirements

Performance

Frequency Monthly

Notes


Use Case Form: Weekly Run

Name Weekly Run

Actor Payroll Clerk

Priority High

Status To be agreed

ExtensionPoints

None

Extends None

Includes Payroll Run


Post-conditions

Flow of Events 1. Use Case begins when initiated by

actor

2. Employees of Type, Hourly are

selected.

3. Employee of Type, Weekly are

added include (Payroll Run)

AlternativePaths


Performance

Frequency Weekly

Notes


Use Case Form: Find Employee

Name Find Employee

Actor payroll Clerk/Human Resources

Priority High

Status To be agreed

ExtensionPoints

None

Extends None

Includes


Has access to I.D. or name

Post-conditions

Makes available Employee Found

Flow of Events 1.Search for Employee Requested.2.If no Employee Found [A1]3.Make Employee found available.

AlternativePaths

Report Employee Not Found


Performance

Frequency

Notes


Use Case Form: Payroll Run

Name Payroll Run

Actor Payroll Clerk, Payroll Printer

Priority High

Status To be agreed

ExtensionPoints

None

Extends None

Includes None


Calling Use Case has selected a list ofEmployees for Processing

Post-conditions

record of each Employee’s Payslip is recorded


Flow of Events 1. The use Case begins during the

Weekly Run or Monthly Run Use

Case

2. For each Employee in list provided

by calling Use Case

a) Create new payslip

b) For each Tax, Company

Deduction

i) Calculate deduction to be

made

ii) Add deduction to payslip

iii) Add deduction to running

total

c) Print payslip

d) Save payslip

3. For each deduction

● Print accumulated total

AlternativePaths


Performance Not an issue. Treat as Batch

Frequency Monthly, Weekly

Notes Reliability is Important

Name Payroll Run


Candidate Object List

Candidate Class/Objects

Reason forElimination Class name

Acme employees SynonymforEmployee

Acme MiningCompany

Outside ofthe system

amount paid Attribute Payslip

annual salary Attribute Monthly Paid employee

check Attributevalue

Employee

clock in time Attribute TimeClockData

clock out time Attribute TimeClockData

companydeductions

Attribute Deduction

country tax CountryTax

currency Attribute Location

deduction Attribute Payslip

deductionpolicies

Method

Earth Dollars Value ofcurrencyattribute

employee Employee


employee details SynomynforEmployee

employeeidentificationnumber

Attribute Employee

employee type Attribute orclass

EmployeeType

excess hoursworked

Derivedattribute

TimeClockData, Location

financial year Synonyn fortax year

flat rate Attribute orclass

FlatRate

gross salary Attribute Payslip

health insurance HealthInsuranceDeduction

hourly employees Synonymforhourly paidemployees

hourly paid Aynonymfor hourlypaidemployees

hourly paidemployees

Class HourlyPaidEmployee




hourly rate of pay Attribute HourlyPaidEmployee

hours worked Attribute TimeClockData

human resources Actor

list of payments Derivedattributes

Payslip

local currency Synonymforcurrency

location Location

month Value oftime

monthly paidemployees

MonthlyPaidEmployee

name Attribute Employee

normal siteworking hours

Attribute Location

overtime rate Attribute Location

pay Attribute Payslip

pay rates Attribute Employee

pay type Attribute Employee




list of payments Derivedattribute

Payslip

payroll clerk Actor

payroll system Theapplication

payslips Payslip

pension scheme PensionSchemeDeduction

percentage ratededuction

Attribute orclass

PercentageRate

Planet Earth Value oflocation

Planet Tax PlanetTax

Planet Zog Value oflocation

planet Attribute ofLocation

pollution tax PollutionTax

site Synonymforlocation

social security tax SocialSecurityTax




system Not relevant

tax deductions Attribute Payslip

tax year Attribute Tax

tiered rates TieredRate

time clock Actor

time clockinformation

TimeClockData

time clock system Actor

total deductions Attribute Payslip

weeklycalculation

Synoym forweeklypayroll

weekly paidemployees

WeeklyPaidEmployee

weekly payroll Use Case

weekly rate ofpay

Attribute WeeklyPaidEmployee




Risk Assessment

Risk is a very subjective subject. Here is the author’s simplified risk

analysis ( using threerisk categories) with some brief reasoning:


Key

● High risk -reason customer needs to see working software, so

these Use Cases will gives a working product.

● Medium risk -will add some more functionality, and the time

interface could be tricky.

● Low Risk -n ot essential or not needed for some time.


Packaging Use Cases By Risk

● If the system was larger, you could do further risk assessment to

break into smaller packages.

● In a real project, you would do several iterations in the inception

and elaboration phases before moving onto the build iterations.

In this case study, time constraints make it imperative to compress

several increments into one.


Activity Diagram

Monthly Pay Run


Note – There are alternation notations for showing a loop.They require

nested activities diagrams. See UML documentation for details.

● You could have shown a nested activity diagram for Calculate

Company Deduction, Calculate Tax Deduction, and Print each

Deduction.


High-Level Packaging


Deployment Diagram


Key Abstractions


Adding Attributes


Adding Associations


Adding Multiplicity


Qualified Associations


Adding Inheritance

● Some of these could have been just attribute values. But they differ

in behavior or attributes, so you have made them extend a base

class.

Note – You have also added a couple of role names.


Additional Classes and Attributes

● You have added new classes and attributes, including an

association class (AmountDeducted ), and including a constraint (

the TierRate must be applied in order).


Adding Aggregation & Composition

● You have based the distinction on ownership, e.g. if the TierRateobjects are only needed for one PlanetTax object. When that

dies, they die too.


Sequence Diagram I

Monthly Payroll Run

● The details of each deduction has been omitted from here.

Calculate pay has also been excluded.


Note – This highlighted a missing class from our diagram, namely the

DeductionSummary , so you have added this.

● Alternatively, you could have derived the values from all of the

Timeslips to avoid creating this extra class. However, you would

then have had to go back and edit our Use Case Form for

PayrollRun etc.


Sequence Diagram II

Monthly Payroll Run Showing Delegation


Sequence Diagram III

For Social Security Tax Calculations

● One of the many alternative Sequence Diagrams for the Monthly

PayrollRun Use Case.

● This one uses some delegation. The Deduction object will add

directly to the Timeslip object, and will do its own printing.


Sequence Diagram IV

Revised for Monthly Payroll Run

● Shows missing interaction.

● In design, you can choose to do this with a Constructor.


State Transition Diagram

For Payslip Class

● It shows that you have missed an important interaction in our

sequence diagram( namely to initialise the pay details ).

● It also highlights that you should ensure that you cannot change

the details once saved.


Removing Association Class

● You have removed the association class by putting the class

between the two associated classes .This has removed the many to

many relationship.


Revised Logical Packaging

● As the diagrams are getting complicated, you need to look at them

in packages. Here are the two Business Model Packages, and one

new Controller Package.


Deduction Logical Packaging

● You have included both Tax and Company Deductions in one

package. This is contrary to the original planned packages.

This has been done this for the purpose of brevity on the course.


Employee Logical Packaging

● We have included the location classes here.In practice, they

perhaps should be in a separate package.

● One option here would be to delegate the Pay to a PayType,

Monthly, Weekly etc would then inherit from that class, thus

making it easy for an Employee to change their PayType.

However this was not in the specification, so you will not

complicate the diagram here.


Miscelleanous Notes and Changes

● The attribute monthlyCharge PensionDeductions was changed to

annualCharge, so it can apply to different Employees Pay Types.

● The Domain expert points out that the SiteOverTimeRate will

change, therefore you need to record the date of the change and

store a list.

● Having decided to keep the Employee as the base class for

different types, you will end up with this being abstract.

● The scoped down problem doesnt need to keep a history of salary

changes, or timeslips. So once pay is processed the Timeslip

objects are destroyed.

● The hours works are integral.

● Payslip objects do need to be kept.


Adding Delegation

● The class CompanyDeduction served no purpose so you have

deleted it.

● Given that several taxes and other deductions share common

strategies of calculating deductions, you have delegated the

common features, using the Strategy Pattern.

● You can use an Abstract Factory Pattern to set up the correct

deduction strategy for the tax, or deduction.

This is just one solution, there are many others, some more

flexible, however you are trying to keep the scope limited.


● The Deduction, Tax, and DeductionStrategy are all abstract classes.

● We have not shown CountryTax to keep diagram clearer, but it still

exists.


Monthly Pay Run

Sequence Diagram in Design

● This is one sequence of events for the Monthly Pay Run.


Pay Run

Sequence Diagram for Pay Run in Design

● This is just one sequence of events for the Pay Run.


Calculate Deduction

Sequence Diagarm In Design

● This is just one sequence of events for the Pay Run.

● This is part of the Pay Run Uses Case.


Tiered Rate Deduction

Sequence Diagram in Design

● This is just one sequence of event.

● This is part of the Pay Run Uses Case.

● Although not part of the current iterations, above is the sequence

diagram for calculating tiered deductions.

● The class TieredRate now performs the behaviour originally

given to the PlanetTax class.


State Transition Diagram

For Payslip Class


Activity Diagram

For Monthly Pay Run


Pay Run Package I

Simple Class Diagram


Pay Run Package II

Pay Run Package Class Diagram


Employee Package I

Simple Employee Package Class Diagram


Employee Package II

Employee Package Class Diagram


Deduction Package

Deduction Package Class Diagram


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